At the present time, at least in Canada, most milk and other dairy products are sold in disposable containers, e.g. cardboard cartons or plastic bags. In some areas, reusable glass bottles are used, but this is a relatively small part of the whole market. Nonetheless, in view of the increasing environmental concerns regarding disposable packaging, the use of the glass bottles for milk and other dairy products is increasing rapidly, currently, at an annual rate of approximately 25%.
A problem arises with providing a simple and economical closure for glass milk bottles. A variety of different closures are known. One type with which the applicant is familiar and currently produces is formed from a paper foil laminate. A cap is a disk form cut from laminate and then crimped around the neck of a milk bottle. It thus forms a top, circular, closure portion, with a shirt portion depending downwardly. The skirt portion is crimped against the neck of the bottle. In a variant, a cardboard disk is mounted to the top of the closure. The top of the closure is then dished down inside the neck of the bottle, so that the cardboard disk is within the neck of the bottle.
Whilst this type of closure is relatively simple and economical, it suffers from a number of disadvantages. First, it does not provide any true evidence of tampering with the container. It is conceivable that someone could remove the closure, and somehow tamper or interfere with the contents of the bottle, and then replace the closure. Further, whilst in normal use, the closure can be replaced after it has been opened, it does not provide wholly satisfactory resealing of the bottle by simply being placed on it.
It is desirable that a closure for a glass milk bottle, and other containers, should meet two requirements. First, it should provide clear tamper evidence, of any tampering of the bottle or its contents, which preferably should be readily externally visible. This then enables a consumer in a store to immediately ascertain whether the bottle has been tampered with or not, without the necessity for removing any external cap or cover member. Secondly, the closure should enable the bottle or other container to be satisfactorily resealed, so that where only part of the contents are used, it can be resealed and retain the remaining contents in good condition.
Further, for a two-part closure, i.e. one which includes an inner seal effecting a primary closure of the container and a secondary outer cap or closure, it is desirable to have some means to prevent caps being switched between different bottles or containers. For example, for dairy products, it is known for unscrupulous consumers to switch caps between products of different price, e.g. 2% milk and cream, in order to be able to purchase the more expensive product at a lower price.
There are a wide variety of conventional tamper-evident closures on the market. These are generally unsuitable for glass bottles. Many of these are in the form of plastic-moulded caps. In one common design, a screw cap is secured to a ring by a number of small, radial spokes. The ring engages part of the bottle so that when the cap is unscrewed the spokes shear, thereby giving an indication that the container has been opened. This cannot be used on glass milk bottles, since they do not include a screw thread, and since the tolerances obtainable with glass would not permit the cover to always securely engage the bottle.
Another design employs a collar connected to a cap by an annular strip, which extends through slightly less than a full circle, to leave the cap secured to the collar by a short connecting strip. The strip is provided with tab, to enable it to be removed, thereby largely detaching the cap from the collar. The cap can then be hinged upwardly to open the bottle, whilst remaining attached to the collar at one edge. Yet another design is a simple plastic cap with a pull ring. Such arrangements again require fairly tight tolerances on the bottle neck, and this is not readily or routinely achieved with a glass milk bottle.
It is also desirable that any primary or inner seal for the container or bottle should be readily removable, and should be capable of simple and economic manufacture and mounting on the container. It is well known to provide a foil closure seal to the neck of a container, although this is not routinely done with glass bottles since it is difficult to obtain an adhesive that provides a good seal to glass. Many such closures are provided with some sort of tab to facilitate removal of the foil. Where an outer cap is provided, the tab is usually folded over on top of the main body of the foil, so as not to interfere with screw threads, etc. which secure the cap to the bottle neck.
U.S. Pat. No. 4,155,439 discusses in detail the production of a foil closure with a folded pull tab. As this patent shows, complex machinery is required to form the closure and fit it to the container. A circular table or platform is provided, in which the containers are placed. The table is then rotated, to move each container through numerous different stations. At each station, a different operation is performed. The closure itself is stamped from a strip of foil, and then the tab has to be folded up on top of the main portion of the closure. This requires a complex sequence or operation. To set up such machinery for a particular production run is time consuming and expensive.
It is should also be noted that additional problems are also encountered with such a technique. Firstly, the presence of the inwardly folded tab can affect the sealing by means of induction heating. Induction heating relies upon the generation of currents to heat the foil. The presence of the tab affects the electrical properties locally, and can result in improper sealing. As discussed in an article by Bill Zito in the August, 1986 issue of Food and Drug Packaging, the current tends to follow the actual periphery of the tab. Also, the folded tab can stick to the inside of the cap, which then requires a silicon liner or the like. The induction sealing technique further relies upon the fact that the foil closure is pressed against the neck of the container by the cap. For the folded tab, there may not be even pressure applied to the foil closure which again can result in an imperfect sealing.
With such a folded tab, there is no external evidence of any tampering with the container, so that strictly a consumer needs to remove the screw cap or the like to ascertain that the inner seal is intact. Further, there is nothing to prevent a consumer switching caps between containers or bottles.
As mentioned above, it is commonly known to provide a foil closure with some sort of tab extending out from the neck of the container, to facilitate removal of the foil. Further, instead of folding the tab on top of the main body of the seal, it is known to leave it extending down between the neck of the bottle and the cap. U.S. Pat. Nos. 3,032,325 and 4,209,126 both show a tab which is thus sandwiched between the side wall of the cap and a bottle neck.
It has further been recognized that, where a foil inner seal or the like is provided in combination with a secondary, exterior cap, then to a casual purchaser, there is no clear indication that the inner seal is intact and has not been tampered with. Indeed, a purchaser of a product may not discover that the seal is broken until they come to open and use the product. Thus, U.S. Pat. Nos. 4,576,297 and 4,579,240 show a cap bonded to an inner seal in such a manner that removal of the cap alone ruptures the seal. The cap itself is transparent or translucent, so that a purchaser or first user can check to see that the inner seal is intact. As soon as the cap is removed, the bond between the cap and the inner seal at least is ruptured, thereby providing an indication that the cap at least has been removed or tampered with.
European published applications 109592 and 111900 similarly provide an indication that a cap has been removed or tampered with, so that a purchaser or user can check the integrity of the primary seal, without having to remove the cap. European published application 109,592 further relies upon a colour change to provide such an indication.
However, all these earlier patents rely on a relatively complex combination between the cap and the inner seal. Further, they do not provide any tab or the like for removing the inner seal. Whilst the bond between the cap and the inner seal may be ruptured, to provide the necessary indication of cap removal or displacement, this does not necessarily remove the inner seal. Accordingly, the user is still left with the problem of detaching the inner seal from the neck of the container.